Force-measuring apparatus for use in a well bore pipe string

ABSTRACT

In the representative embodiment of the apparatus of the present invention disclosed herein, a pair of force-measuring sleeves are telescoped together and coaxially mounted on a tubular body with their opposite ends engaged with opposed shoulders on the body so that, when the body is coupled into a well bore pipe string, even minor torsional or longitudinal forces acting on the body will cause proportional movement of the sleeve members in relation to one another. To detect these forces, a loop-like deformable member having circumferentially-spaced rings joined together by elongated strips or bars is coaxially disposed on the tubular body with the spaced rings tightly clamped between opposed shoulders on the sleeve members. Two or more arrays of strain gages respectively mounted on the rings and bars forming the loop are cooperatively arranged for providing electrical signals which are representative of the longitudinal and torsional forces imposed on the tubular body tending to dimensionally distort the loop-like member.

United States Patent 91 Anderson [451 Feb. 11, 1975 FORCE-MEASURINGAPPARATUS FOR USE IN A WELL BORE PIPE STRING [75] inventor: Ronald A.Anderson, Houston, Tex.

[73] Assignee: Schlumberger Technology Corporation, New York, NY.

[22] Filed: Nov. 19, 1973 [21] Appl. No.: 417,005

Related [1.8. Application Data [62] Division of Ser. No. 359,829, May14, 1973,

Primary Examiner.lerry W. Myracle Attorney, Agent, or Firm-Ernest R.Archambeau, Jr.; William R. Sherman; Stewart F. Moore zv lg [57]ABSTRACT In the representative embodiment of the apparatus of thepresent invention disclosed herein, a pair of forcemeasuring sleeves aretelescoped together and coaxially mounted on a tubular body with theiropposite ends engaged with opposed shoulders on the body so that, whenthe body is coupled into a well bore pipe string, even minor torsionalor longitudinal forces acting on the body will cause proportionalmovement of the sleeve members in relation to one another. To detectthese forces, a loop-like deformable member havingcircumferentially-spaced rings joined together by elongated strips orbars is coaxially disposed on the tubular body with the spaced ringstightly clamped between opposed shoulders on the sleeve members. Two ormore arrays of strain gages respectively mounted on the rings and barsforming the loop are cooperatively arranged for providing electricalsignals which are representative of the longitudinal and torsionalforces imposed on the tubular body tending to dimensionally distort theloop-like member.

25 Claims, 6 Drawing Figures SHEET 1 BF 2' PATENTEB FEB I I I975 SIGNALDETECTOR TURBINE GE NgRA TOR l FORCE-MEASURING APPARATUS FOR USE IN AWELL BORE PIPE STRING This application is a division of my copendingapplication Ser. No. 359,829, now abandoned, filed May 14, 1973, forWell Bore Force-Measuring Apparatus".

Those skilled in the art will, of course, appreciate that it is of greatvalue to know the axial load as well as the applied torque on the drillbit during the drilling of a well. In addition to being useful incontrolling the direction or inclination of the borehole as it is beingdrilled, such measurements are also of great significance in achievingthe most efficient and economical drilling program for that well. Forexample, it is a common practice to pre-schedule the drilling programfor a given well so that the most efficient drilling speeds, bit loads,and drill bits will be used for drilling each of the several formationintervals which are expected to be encountered before the boreholereaches its specifled depth.

Heretofore, many long-standing techniques have been employed for eitherestimating or empirically measuring the bit torque and weight-on-bitfrom the surface. Those skilled in the art will, of course, recognizethat any surface measurements which of necessity must be extrapolated toderive an assumed bit torque or weight-on-bit are subject to manypotential errors arising from such factors as the friction of the drillstring against the borehole wall. Accordingly, it is widely recognizedthat knowledge with a fair degree of precision of the actualweight-on-bit and bit torque at any given time during a typical drillingoperation is of far greater benefit than simply estimating these loadsto optimize such operations.

To obtain measurements representative of the actual weight-on-bit loadas well as the bit torque, various force-measuring devices have beenpreviously proposed for use with different types of signaling systemssuch as the downhole signaling systems shown in Pat. No. 3,736,558 orPat. No. 3,764,970 for transmitting encoded acoustic data signals to thesurface through the circulating mud stream in the drill string. One ofthe more common of these force-measuring devices employs an array ofsuitable strain gages mounted on one of the several conventional drillcollars which are customarily connected in a typical drill stringimmediately above the drill bit. Those skilled in the art willrecognize, however, that such arrangements are essentially soinsensitive that only major changes in the load conditions can bedetected. Quite simply, the problem is that with the typicalheavy-walled drill collars used in present-day drilling operations, theamount of deformation experienced thereby in response to changes ineither torsional or axial loadings are so minute that even the mostsophisticated strain gages will simply fail to adequately respond.

To counter these major disadvantages, various proposals have been madefor increasing the output response of such strain gages. For example, asshown in FIG. 3 of Pat. No. 2,422,806, a conventional forceresponsivetransducer is mounted on an upright post and this assembly is mountedbetween two opposed shoulders defined by a shallow recess in the wall ofthe drill collar to provide output signals representative of thedeformations of the slightly-reduced wall section. Although thisarrangement offers slightly more sensitivity, the degree of deformationin this wall section which might ordinarily occur during a typicaldrilling operation is nevertheless so extremely small that the resultingoutput measurements are still somewhat insensitive to anything short ofsignificant changes in the load conditions on the drill bit.

An alternative proposal is found in Pat. No. 3,686,942 in which anindependent load-bearing member carrying an array of strain gages iscooperatively telescoped within a stronger load-bearing member andarranged to carry all of the axial and torsional loads acting on thedrill bit so long as these loads remain within a predetermined rangewhich is well within the useful strength of the weakertransducer-bearing member. Should, however, the loads on the drill bitexceed the maximum design capabilities of the transducerbearing member,the weaker load-carrying member will be moved into engagement with acooperative shoulder on the stronger load-carrying member so that theentire load will thereafter be imposed on this paralleling memberthereby relieving the weaker member of these potentially-damaging loads.Although this particular arrangement offers manyadvantage not foundheretofore, those skilled in the art will recognize, nevertheless, thatsince this transducer-bearing member must still be capable of supportingsignificant axial or torsional loads, the strain gages will still berelatively insensitive to minor load changes.

Accordingly, it is an object of the present invention to provide new andimproved force-measuring apparatus for reliably providing accuratemeasurements of even minor axial or torsional laods which may act on awell bore pipe string such as those imposed on a drill string during thecourse of a drilling operation.

This and other objects of the present invention are attained byarranging a force-responsive member having a spaced pair of deformablerings which are joined together by at least one deformable member andclamping the opposite edges of these rings between opposed shoulders ona tubular load-bearing body which is adapted for coupling in a string ofwell pipe such as a drill string. Force-responsive transducer means arecooperatively mounted on the force-responsive member. In this manner,upon application of either axial or torsional loads on the load-bearingbody, even minute load-inducted deformations of the load-bearing bodywill induce proportional deformations in the forceresponsive member forproducing greatly-increased output signals representative of strainwhich, is desired, may be transmitted to the surface.

The novel features of the present invention are set forth withparticularity in the appended claims. The invention, together withfurther objects and advantages thereof, may be best understood by way ofthe following description of exemplary apparatus employing theprinciples of the present invention as illustrated in the accompanyingdrawings, in which:

FlG. 1 shows new and improved force-measuring apparatus employing theprinciples of the present invention as it will appear while arranged ina drill string during the course of a typical drilling operation;

FIG. 2 is an enlarged view of the preferred embodiment of theforce-measuring apparatus shown in FIG. 1;

FIG. 3 is an isometric view of a preferred embodiment of theforce-responsive element used in the new and improved force-measuringapparatus shown in FIGS. 1 and 2;

FIGS. 4A and 4B are developed views of the forceresponsive element ofFIG. 3 respectively illustrating its operation in the absence of torsionand under torsional loads; and

FIG. 5 depicts a preferred embodiment of electrical circuitry which maybe used in conjunction with the apparatus of the present invention.

Turning now to FIG. 1, a downhole data-signaling tool such as either ofthose shown in Pat. No. 3,736,558 or Pat. No. 3,764,970 is depictedcoupled to the lower end of a typical drill string 11 made up of aplurality of pipe joints l2 and one or more drill collars 13 and havinga rotary drill bit 14 dependently coupled thereto for excavating aborehole 15 through various earth formations as at 16. As the drillstring 11 is rotated by a typical drilling rig (not shown) at thesurface, substantial volumes of the drilling fluid or so-called mud" arecontinuously pumped downwardly through the tubular drill string and thetool 10 and discharged from the drill bit 14 for cooling the bit as wellas carrying borings removed by the bit to the surface as the mud isreturned upwardly along the borehole l5 exterior of the drill string. Asis typical, the mud stream is circulated by employing one or morehigh-pressure mud pumps (not shown) which continuously draw the fluidfrom a storage pit or surface vessel (not shown) for subsequentrecirculation by the mud pumps. It will be appreciated, therefore, thatthe circulating mud stream flowing through the drill string 11 serves asa transmission medium that is well suited for transmitting acoustic datasignals from the data-signaling tool 10 to the surface at the speed ofsound in the particular drilling fluid.

In accordance with the principles of the present invention, new andimproved force-measuring apparatus 17 is preferably arranged in thedrill string 11 between the well tool 10 and the bit 14 and electricallycoupled to appropriate measurement encoder means 18 operatively arrangedin the data-signaling tool for producing a series of electrical codeddata signals that are representative of the forces being imposed on thedrill bit. it will, of course, be appreciated that the data-signalingtool 10 can also be coupled to one or more conditionresponsive devices,as at 19 and 20, cooperatively arranged on the tool for measuring suchdownhole conditions as the pressure, the temperature, or the resistivityor conductivity of either the drilling mud or the adjacent earthformations as well as various formation conditions or characteristicswhich are typically obtained by various commercial logging tools. Theseconditionmeasuring devices 19 and 20 are also cooperatively coupled tothe measurement encoder 18 for independently producing electricalsignals that are each representative of the particular downholeconditions or formation properties which are being measured. It will beunderstood, of course, that the measurement encoder 18 will becooperatively arranged so as to sequentially obtain each of the severaldesired measurements for independently transmitting a representativeencoded signal to the surface. Although a self-contained battery orpower supply can be employed, as shown at 21 it is preferred to employ areaction-type turbine driving a generator for utilizing the circulatingmud stream passing through the tool 10 as a motivating source togenerate electrical power for operating the tool.

The data-signaling tool 10 is preferably arranged as described ingreater detail in Pat. No. 3,764,970 which is incorporated by referenceherein. As described in that patent, the tool 10 includes asignal-transmitting unit 22 having an electrical motor 23 which iscoupled by control circuitry 24 to the encoder l8 and opera- 5 tivelyarranged to respond to its coded output signals for rotatively drivingan acoustic signaler 25 by way of a typical gear train 26 tosuccessively interrupt or obstruct the flow of the drilling fluidthrough the drill string 11. The resulting acoustic signals produced bythe acoustic signaler 25 will be successively transmitted to the surfacethrough the mud stream flowing within the drill string 11 as sequentialencoded data signals indicative of the force measurements provided bythe force-responsive apparatus 17 as well as the one or more downholeconditions or formation characteristics respectively sensed by thecondition-measuring devices 19 and 20. As these acoustic data signalsare succes sively transmitted to the surface, they are detected andconverted into meaningful indications or records by suitable acousticsignals detecting-and-recording apparatus 27 such as disclosed in eitherPat. No. 3,309,656, Pat. No. 3,488,629, Pat. No. 3,555,504, or Pat. No.3,716,830 or Pat. No. 3,747,059, each of which are incorporated byreference herein. It will, of course, be further recognized that theacoustic signaler 25 could also just as well be the signaler describedin either Pat. No. 3,764,968 or Pat. No. 3,764,969, each of which areincorporated by reference herein. Similarly, the signaltransmitting unit22 could be any of the new and improved downhole units described ineither Pat. No. 3,309,656, Pat. No. 3,71 l,825, Pat. No. 3,713,089 orPat. No. 3,763,558, each of which are incorporated by reference herein.

Turning now to FIG. 2, a cross-sectioned elevational view is shown of apreferred embodiment of the forceresponsive apparatus 17. As seen there,the forceresponsive apparatus 17 preferably includes a thickwalledtubular sub or body 28 which is cooperatively arranged in a typicalmanner with appropriate end connections, as at 29 and 30, to allow thesub to be tandemly coupled at a desired location in the drill string 11.The sub 28 includes an axial fluid passage 31 for conducting thedrilling fluid flowing through the drill string 11 to the drill bit 14therebelow. For convenience of design, in the preferred embodiment ofthe force-responsive means 17, the tubular body 28 is arranged to havean external diameter substantially equal to the external diameter of theadjacent body 13 of the tool 10 and the internal bore 31 of the tubularsub is moderately enlarged, as at 32, so as to leave a reducedthicknesscentral wall portion, as at 33, of sufficient thickness and strength towithstand the rigorous loads normally experienced during the drilling ofa typical well bore.

1n the preferred embodiment of the new and improved force-responsiveapparatus 17, a loop-like loadresponsive member or circular band 34 suchas the one to be subsequently described by reference to FIG. 3 iscoaxially disposed in the enlarged body cavity 32 with its oppositeedges compressively retained between and frictionally engaged withopposed shoulders 35 and 36 respectively formed around upper and lowersleeve members 37 and 38 coaxially mounted in the internal bore 31 ofthe body 28. Although other arrangements within the purview of thepresent invention could just as well be employed, it is preferred toreleasably secure the load-bearing sleeves 37 and 38 to the tubular body28 in such a manner that a selectively-adjustable compressive load canbe initially imposed on the loadresponsive element 34.

Accordingly, as illustrated in FIG. 2, the upper end of the upper sleeve37 is firmly abutted against a downwardly-facing shoulder 39 formed inthe internal bore 31 of the body 28 just above the enlarged cavity 32.To be certain that the upper sleeve 37 is tightly secured to the body 28for transmitting downwardly-acting axial or compressive loads as well astorque from the upper portion of the body to the top edge of theloadresponsive loop element 34, the upper end of the sleeve is inwardlyenlarged, as at 40, and adapted for engagement between the body shoulder39 and an upwardlyfacing outwardly-enlarged shoulder 41 arranged on anannular retainer member 42 which is threadedly secured, as by threads43, within the internal bore 31 above the enlarged body cavity 32. Itwill be appreciated, therefore, that by virtue of this arrangement, theretaining 42 can be readily adjusted as required to effectively securethe upper end of the upper sleeve 37 tightly to the sub body 28 withoutotherwise having to force the sleeve longitudinally into a desiredposition by imposing a compressive load onto the sleeve through theload-responsive element 34. The significance of this will subsequentlybe explained.

The lower sleeve 38 is similarly arranged so that it may be adjustablysecured tightly to the lower portion of the sub body 28 without imposingan unwanted load onto the load-responsive element 34. To accomplishthis, the lower end of the lower sleeve 38 is outwardly enlarged, as at44, for engagement with a downwardlyfacing companion shoulder 45 on thebody 28 just below the enlarged body cavity 32. An adjusting nut orannular retainer 46 is threadedly secured, as by threads 47, within theinternal bore 31 below the enlarged cavity 32 in the sub body 28.Although a locking orjam nut could just as well be employed, it ispreferred to arrange a depending lug 48 on the threaded retainer 46 andhave a set screw 49 in the lug adapted to be laterally moved intoengagement with the internal wall of the body 28 once the lower retaineris properly positioned.

It should be noted at this point that in the preferred embodiment of theforce-measuring apparatus 17 shown in FIG. 2, the upper retainer 42 iscooperatively arranged to tightly engage the upper sleeve 37 against thebody 28 as required without imposing any load on the load-responsiveelement 34. On the other hand, once the upper sleeve 37 is locked intoengagement with the body shoulder 39 and the load-responsive element 34is in position, movement of the lower sleeve 38 into engagement with thebody shoulder 44 will tend to compress the load-responsive element.Although it is necessary to compressively load the load-responsiveelement 34 for securing it against slippage or circumferential movementin relation to the upper and lower sleeves 37 and 38, it is oftendesired to urge the lower sleeve against its mating body shoulder 45with more compressive force than is desired to impose on theload-responsive loop element. Accordingly, to allow for suchdifferences. it is often found that by placing one or more flat washersor shims, as at 50, of various selected thicknesses between theoutwardly-enlarged sleeve end 44 and the body shoulder 45, the lowerretainer 46 can be adjusted so as to adequately clamp theload-responsive element 34 between the two sleeve shoulders 35 and 36and still urge the lower sleeve 38 and the shim or shims against thebody shoulder 45 with sufficient force to secure the lower sleeveagainst turning with relation to the body 28.

It will be reocognized, of course, that as compressive forces areaxially applied on the tubular body 28,, its overall length will beproportionally shortened in direct relation to the magnitude of the fullcompressive load. Thus, inasmuch as the thin loop-like element 34 isrigidly clamped at its upper and lower edges to the sleeves 37 and 38and, by way of the sleeves, to the upper and lower portions of thetubular body 28, any axial deformation of the body will becorrespondingly transferred directly to the load-responsive element. Inother words. if a given axial load is sufficient to shorten the tubularbody 28 by 0.1-inch, for example, the thin-walled loop 34 must also belongitudinally shortened or compressed by 0.1-inch since the large ormajor'portion of any axial deformation acting on the sleeves 37 and 38will be accommodated by or concentrated on the loadresponsive element.Thus, for a given axial force and the resulting longitudinal deformationof the loadbearing tubular body 28, most of the correspondingdeformation which must take place between the opposed shoulders 35 and36 of the upper and lower sleeves 37 and 38 will be concentrated in therelatively short vertical height of the load-responsive element 34.Simple mathematical analysis will, of course, show that the amount ofdeformation which will be experienced by the thin load-responsiveelement 34 will be proportional to the ratio of the stiffness of theupper and lower sleeves 37 and 38 to the stiffness of the thinnerloadresponsive sleeve or loop.

Those skilled in the art will appreciated, of course, that a substantialdeformation will be experienced by this thin load-responsive element 34even under relatively minor axial loads on the tubular body 28 causingonly a very minor deformation which must be distributed uniformly alongthe full length of the tubular body. It may be said, therefore, thatthis unique arrangement provides a significant amplification of theamount of strain which will be experienced by the thin load-responsiveelement 34 in comparison to the strain imposed on the body wall 33thereby causing a much greater sensitivity to longitudinal deformationor movement at this location than will be realized at any other portionof the new and improved force-measuring sub 17. Accordingly, fomeasuring axial loads on the drill bit 14, as will be subsequentlyexplained, forceresponsive transducer means such as plurality of typicalstrain gages (not shown in FIG. 2) are mounted at selected locations onthe force-responsive element 34 for providing signifcant output signalsin response to even minor axial deformations of the load-bearing sub 17.

Turning now to FIG. 3, an isometric view is shown of a preferredembodiment of the load-responsive element 34. As illustrated, theload-responsive element 34 is preferably formed as an integral band orthin-walled loop of a suitable metal having a pair of generallycircularenlargements 51 and 52 which are perforated, as at 53 and 54, andspaced. apart and joined to one another by deformable links such as apair of semicircular or curved strips 55 and 56 having a width orvertical height somewhat less than the outside diameter of the annularenlargements. By comparing FIGS. 2 and 3 it will, of course, berecognized that it is only the upper and lower tangential points on eachedge of the enlarged annular portions 51 and 52 of the loadresponsiveelement 34 which are respectively in contact with the opposed shoulders35 and 36 on the upper and lower sleeves 37 and 38. Thus, whenever anaxial compressive load is imposed on the tubular body 28, there will bea proportional load acting on the enlarged annular portions 51 and 52tending to compress or flatten them.

It will, of course, be appreciated that vertical compressive loads onthe enlarged annular portions 51 and 52 will develop proportionaltensile stresses or strains on the fibers immediately adjacent to thetop and bottom surfaces of each hole 53 and 54. It will be furtherrecognized that there will be proportional compressive stresses orstrains on the fibers immediately adjacent to the side surfaces of theholes 53 and 54 in each annular portion 51 and 52. Accordingly, inkeeping with the objects of the present invention in the preferredembodiment of this invention, tension-responsive strain gages, as at57-60 in FIG. 4A, are respectively secured at the top and bottom of theholes 53 and 54 in the enlarged portions 51 and 52 andcompression-responsive strain gages, as at 61-64, are respectivelysecured at the sides of these holes. Thus, each of these several straingages 57-64 will respectively exhibit a changing or varying electricalcharacteristic such as resistance which will be proportional to theaxial load acting on the forceresponsive element 34. It will, of course,be recognized that all of the strain gages 57-64 will uniformly respondto deformations caused by thermal conditions and other extrinsic forcesnot related to the axial loads on the drill string 11. Thus, tocompensate for these extrinsic forces, the strain gages 57-64 arearranged in an electrical bridge that will subsequently be discussed byreference to FIG. 5.

Particular recognition should be given to the significant amplificationof strain or stress provided by the unique arrangement of theforce-responsive element 34. In addition to the strain amplificationpreviously discussed in relation to the ratio of the strain in theload-responsive member 34 to that in the body wall 33, the geometry ofthe rings or annular portions 51 and 52 as such provides a significantadditional strain amplification. Considering first of all the stress orstrain acting on fibers at the upper and lower surfaces of the holes 53and 54, it will be recognized that these surfaces will be subjected to asubstantial tensile stress or strain as a compressive load on the toolbody 28 tends to flatten the rings 51 and 52. Similarly, it can also bedemonstrated that the fibers along the sides of the holes 53 and 54 willbe subjected to a substantial compressive strain in response to acompressive load tending to flatten the rings 51 and 52. Thus, a stillfurther strain amplification is provided by the new and improvedforceresponsive element 34 when the force-measuring apparatus 17 issubjected to an axial compressive load.

As previously mentioned, it is also of considerable importance to knowthe actual torque being applied to the drill bit 14 during the courseofa typical drilling operation. it will be recognized, therefore, thatwhen the drill bit 14 is set on the bottom of the borehole l5 and atorsional force is applied to the drill string 11, the upper portion ofthe body 28 above its enlarged cavity 32 will be angularly advanced ortwisted about the longitudinal axis of the body so as to move the upperbody portion in relation to the lower portion of the body below thecavity through an angle that is proportional to the magnitude of theapplied torque. Thus, since the sleeves 37 and 38 are tightly engagedwith the body 28, the upper sleeve will tend to rotate in relation tothe lower sleeve as torque is applied through the drill string 11 andthe force-measuring apparatus 17 to the drill bit 14.

As illustrated in the exaggerated developed view in FIG. 48, therefore,torque will cause the upper sleeve shoulder 35 to be moved in relationto the lower sleeve shoulder 36 as represented by the arrows 65 and 66.Accordingly, as shown by the arrows 67 and 68, this relatively angularmovement between the upper and lower sleeves 37 and 38 caused bytorsional loads will tend to roll each of the enlarged annular portions51 and 52 respectively about an axis perpendicular to and passingthrough the center of each of the holes 53 and 54. The extent of thisrotation will, of course, be directly related to torque. This tendencyof the enlarged portions 51 and 52 to roll will, however, be resisted bytheir interlinking strips 55 and 56 so that these strips will bedistorted in a manner similar to that illustrated in the exaggerateddeveloped view of the forceresponsive element 34 shown in FIG. 4B. Thus,it is preferred to make the links 55 and 56 relatively flexible so thatthey will readily deflect and impose only a minimum restraint on therotation of the rings 52 and 53. It will be recognized, of course, thatany resistance to rotation of the rings 52 and 53 will imposecounteracting stresses which will be undesirably sensed by thetransducers 57-64.

Various techniques may be provided for relating the rotation of therings 52 and 53 to the magnitude of the torque on the drill string 11causing this rotation. However, those skilled in the art will appreciatethat the magnitude of the deflection or distortion of the strips orlinks 55 and 56 is directly related to the magnitude of any torsionalforces and that this deflection of the strips will be most pronounced atabout their respective one-quarter and three-quarter points. Moreover,in keeping with accepted strain analysis techniques, where, for example,the rotation of the drill string 11 results in a downward bowing at theone-quarter point and an upward bowing at the three-quarter point of theinterlinking strips 55 and 56, the fibers lying along the convex edgesof each bulge will be proportionally tensioned and the fibers runningalong the concave edges of each bulge will be proportionally compressed.The opposite result would, of course, occur should the usual rotation ofthe bit 14 be in the opposite direction.

Accordingly, to measure these compressive forces for the usual directionof bit rotation, one or more compression-responsive strain gages, as'at69-72, are respectively placed on the appropriate edges of theinterlinking strips 55 and 56 at about their respective onequarter andthree-quarter points. Similarly, one or more typical tension-responsivestrain gages, as at 73-76, are respectively mounted on the upper andlower edges of the interlinking strips 55 and 56 opposite each of thecompression-responsive gages 69-72. Thus, upon application of torque tothe drill string 11, those of the tension-responsive strain gages 73-76which are subjected to tensile forces will exhibit a correspondingchange in their respective electrical characteristic which isproportional to the deflection of the strips 55 and S6 and, therefore,to the amount of torque. In a like manner, the characteristic of thecompression-responsive strain gages 69-72 will also change points willbe greatly reduced and the strain in those portions of the stripsadjacent to these slots will be greatly accentuated so as to provide anamplified output from the transducer 69-76. In this manner, the outputsignals provided by the torque-responsive strain gages 69-76 will begreatly increased over what would otherwise be provided if it were notfor the particular unique arrangement of the present invention.

The various devices used heretofore for measuring torque andweight-on-bit have typically either ignored or taken less than adequatemeasures for limiting or avoiding the effects of pressure differentialswhich must otherwise affect the accuracy of the force measurements.Those skilled in the art will, of course, appreciate that there isnormally a substantial pressure differential the drilling fluid flowingthrough the drill string 11 and the fluid in the borehole l exterior ofthe drill string. Where there are downhole signaling devices such asthose previously described herein for transmitting acoustic signals tothe surface, the additional pressure pulses produced by these signalingdevices will also increase the pressure differential acting across theforce-measuring apparatus 17. Thus, if no preventative measures aretaken for protecting or isolating the force-responsive element 34, anincreased pressure in the longitudinal bore 31 will tend tocircumferentially enlarge as well as elongate the tubular body 28 andthereby impose a corresponding deformation on the force-responsiveelement.

Accordingly, to at least minimize this unwanted deformation, as shown inFIG. 2 a thick-walled tube 78 is coaxially extended between the upperretainer member and the lower sleeve and slidably fitted within eachmember so as to not be compressively loaded as the sleeves 37 and 38 andthe retainer members 42 and 46 are being positioned during the assemblyof the forceresponsive sub 17. A fluid sea], as at 79, is mounted aroundthe tube 78 so as to fluidly seal its upper end in relation to the upperretainer 42. Fluid seals, as at 80 and 81, are also arranged to fluidlyseal the upper sleeve 37 in relation to the upper retainer 42 and to theupper portion of the body 28. Since it is necessary to seal the lowerseal 38 in relation to 'only the lower portion of the body 28, a singleseal, as at 82, is sufficient to achieve the objects of the presentinvention.

The lower sleeve 38 is extended, as at 83, so as to be telescopicallyfitted within the upper sleeve 37 and thereby define an annular space 84between the sleeves and the elongated tube 78. To maintain the bodycavity 32 at a pressure which will sufficiently minimize elongation andcircumferential expansion of the tubular body 28 due to pressuredifferentials, the cavity is filled with a suitable hydraulic fluid,such as oil, and pressure-balancing means, such as an annular piston 85mounted in the annular space 84 and coupled by a passage 86 in the tube78, are provided for communicating the pressure of the drilling mudflowing through the internal bore 31 to the body cavity. To allow theoil filling the upper end of the annular space 84 above the piston 85 tocommunicate with the body cavity 32, one or more ports 87 are formed inthe upper sleeve 37. In this manner, it will be appreciated that the oilfilling the upper end of the annular space 84 and the body cavity 32will be maintained at a pressure equal to that of the drilling fluidflowing through the longitudinal bore 31.

It will, of course, be recognized that various types of electricalcircuits may be arranged to measure the respective changes in theelectrical characteristics of the several transducers 57-64 and 69-76.However, as shown in FIG. 5, in the preferred embodiment of the presentinvention, it is preferred to arrange these transducer 57-64 and 69-76into two typical bridge circuits as shown generally at 88 and 89. Itwill be appreciated, therefore, from a comparison of FIG. 5 with FIGS.4A and 48 that the bridge circuits 88 and 89 are arranged to produceseparate output signals at 90 and 91 which are respectivelyrepresentative of the applied axial loads on the body 28 as well as thetorque applied thereto.

Since the bridge circuit 88 is typical and is well known to thoseskilled in the art, it is believed necessary only to point out that theweight-responsive strain gages 57-64 comprising this bridge are arrangedin an additive fashion for providing a maximum output in response todeformation of the load-responsive element 34 caused by direct or actualaxial loads on the body 28. Similarly, as various ones of thetorque-responsive transducers 69-76 change in response to changes in thetorsional loads on the body 28, a correspondingly enhanced output signalwill be produced at the output 91 of the bridge circuit 89.

Accordingly, itwill be appreciated that the new and improvedforce-measuring apparatus 17 of the present invention is particularlyresponsive to both axial and torsional forces for producing much-greateroutput signals than has been possible heretofore. By arranging theforce-responsive element 34 to be particularly susceptible to pronouncedor magnified deformation at the very location of the severalstrain-measuring devices 57-64 and 69-76, the typically-low outputs ofthese devices will be greatly accentuated so as to provide a much widerproportional band or response than would otherwise be possible.Moreover, by arranging the force-responsive element 34 as previouslydescribed, there is no concern that this weak forceresponsive elementwill be damaged by even extreme axial or torsional loads. Additionally,by arranging the force-measuring sub 17 to be pressure balanced, theeffects of changes in temperature or pressure that would otherwise tendto limit the reliability and accuracy of the force measurements aresignificantly minimized.

While only a particular embodiment of the present invention has beenshown and described, it is apparent that changes and modifications maybe made without departing from this invention in its broader aspects;and, therefore, the aim in the appended claims is to cover all suchchanges and modifications as fall within the true spirit and scope ofthis invention.

What is claimed is:

1. Apparatus adapted for sensing loads acting on a pipe string in a wellbore and comprising:

a load-bearing body adapted for coupling to a string of pipe;

a deformable load-responsive member secured in a normal upright positionbetween longitudinallyspaced portions of said load-bearing body andhaving an unrestrained intermediate portion adapted to deform inresponse to increases and decreases in axial loads imposed on saidload-bearing body tending to move said spaced body portionslongitudinally in relation to one another and to tilt in relation to itssaid normal position in response to torsional loads imposed on saidload-bearing body tending to move said spaced body portions angularly inrelation to one another;

first transducer means coupled to said loadresponsive member and havinga measurable characteristic adapted to vary in response to deformationof said load-responsive member occurring upon relative longitudinalmovement between said spaced body portions; and

torque-responsive means including second transducer means coupled tosaid load-responsive member and having a measurable characteristicadapted to vary in response to tilting movements of said load-responsivemember away from its said normal position occurring upon relativeangular movement between said spaced body portions.

2. The load-sensing apparatus of claim 1 wherein at least one of saidmeasurable characteristics is an electrical property; and said firsttransducer means include at least one strain gage mounted on saidintermediate portion of said load-responsive member and exhibiting avarying range of said electrical property in response to strainvariations occurring upon the deforamtion of said load-response memberby axial loads on said loadbearing body.

3. The load-sensing apparatus of claim 2 wherein said torque-responsivemeans include a deformable member projecting laterally from saidintermediate portion of said load-responsive member and cooperativelyarranged to deform in response to tilting movements of saidload-responsive member, and said second transducer means include atleast one strain gage mounted on said lateral member and exhibiting avarying range of said electrical property in response to strainvariations occurring upon the deformation of said lateral member bytorsional loads on said load-bearing body.

4. The load-sensing apparatus of claim 2 wherein said intermediateportion of said load-responsive member is cooperatively curved andarranged to be strained in proportion to the extent of curvature of saidintermediate portion.

5. The load-sensing apparatus of claim 4 wherein said torque-responsivemeans include a deformable member projecting laterally from saidintermediate portion of said load-responsive member and cooperativelyarranged to deform in response to tilting movements of saidload-responsive member, and said second transducer means include atleast one strain gage mounted on said lateral member and exhibiting avarying range of said electrical property in response to strainvariations occurring upon the deformation of said lateral member bytorsional loads on said load-bearing body.

6. Apparatus adapted for sensing loads acting on a pipe string in a wellbore and comprising:

a load-bearing body adapted for coupling in a string of pipe;

a load-responsive member having axially-spaced opposite portionsrespectively secured between longitudinally-spaced portions of saidload-bearing body for normally maintaining said load-responsive memberin an upright position and an unrestrained non-linear intermediateportion cooperatively arranged to deflect in response to axial loadsimposed on said load-bearing body tending to move one of said spacedbody portions longitudinally in relation to the other of said spacedbody portions as well as to shift away from said upright position inresponse to torsional loads imposed on said load-bearing body tending tomove one of said spaced body portions angularly in relation to the otherof said spaced body portions;

first means coupled to said intermediate portion of said load-responsivemember and cooperatively arranged for providing a first output signalproportional to deflections of said intermediate portion of saidload-responsive member occurring upon relative longitudinal movementbetween said spaced body portions caused by axial loads imposed on saidload-bearing body; and

second means coupled to said intermediate portion of saidload-responsive member and cooperatively arranged for providing a secondoutput signal proportional to the extent of movement of saidloadresponsive member away from its said upright position occurring uponrelative angular movements between said spaced body portions caused bytorsional loads imposed on said load-bearing body.

7. The load-sensing apparatus of claim 6 wherein said load-responsivemember is interior of said load-bearing body.

8. The load-sensing apparatus of claim 7 further including:

a sleeve member having upper and lower end portions respectivelyextending between said spaced body portions;

means cooperating with said upper and lower end portions of said sleevemember for defining an enclosed chamber around said load-responsivemember; and

pressure-regulating means cooperatively arranged on said load-bearingbody and adapted for maintaining said enclosed chamber at an elevatedpressure.

9. The load-sensing apparatus of claim 6 wherein said second meansinclude a laterally-oriented deformable member secured between saidload-bearing body and said intermediate portion of said load-responsivemember and cooperatively arranged to deform upon movement of saidload-responsive member away from its said upright position, andtransducer means including at least one strain gage cooperativelyarranged on said deformable member and exhibiting a variable electricalcharacteristic which is proportional to the strain developed in saiddeformable member by deformation thereof.

10. The load-sensing apparatus of claim 6 wherein said intermediateportion of said load-responsive member is symmetrically curved away froman axis passing through said axially-spaced portions of saidloadresponsive member for producing a concentrated strain at about themid-point of said intermediate portion upon deflection thereof; and saidfirst means include at least one strain gage mounted on about saidmid-point of said intermediate portion and exhibiting a variableelectrical characteristic which is proportional to the strain developedin said mid-point of said intermediate portion.

11. The load-sensing apparatus of claim 10 wherein said second meansinclude a laterally-deformable member secured between said load-bearingbody and said intermediate portion of said load-responsive member andcooperatively arranged to deform upon movement of said load-responsivemember away from its said upright position, and transducer meansincluding at least a second strain gage cooperatively arranged on saiddeformable member and exhibiting a variable electrical characteristicwhich is proportional to the strain developed in said deformable memberby deformation thereof.

12. Apparatus adapted for sensing loads acting on a drill bitdependently coupled to a drill string and operatively arranged forexcavating a-borehole and comprismg:

a tubular load-bearing body adapted for tandem coupling in a tubulardrill string and having a longitudinal bore for conducting drillingfluids flowing through such drill string sections;

load-responsive means cooperatively arranged between upper and lowerportions of said loadbearing body and adapted for selectively respondingto compressional loads imposed on said loadbearing body tending to movesaid upper and lower body portions longitudinally in relation to oneanother and to torsional loads imposed on said loadbearing body tendingto move said upper and lower body portions angularly in relation to oneanother, said load-responsive means including a deformable loopcoaxially arranged around an intermediate portion of said load-bearingbody and divided into at least one substantially-rounded compressiblesegment and at least one elongated strip-like bendable segment havingone end coupled toone side of said rounded segment and extendinglaterally therefrom around said intermediate body portion, first andsecond means respectively securing the upper and lower edges of saidrounded segment to said upper and lower body portions for alternativelycompressing said rounded segment upon longitudinal movement of saidupper and lower body portions toward one another and rolling saidrounded segment to an inclined position upon relative angular movementbetween said upper and lower body portions so as to correspondingly tiltsaid strip-like segment;

first electrical transducer means cooperatively arranged on said roundedsegment and adapted for exhibiting a varying electrical characteristicproportional to the magnitude of compressional forces applied to saidrounded segment; and

second electrical transducer means cooperatively arranged on saidstrip-like segment and adapted for exhibiting a varying electricalcharacteristic proportional to the magnitude oftorsional forces appliedto said rounded segment.

13. The load-sensing apparatus of claim 12 wherein said rounded segmentis annular so that compressional forces imposed thereon will developedenhanced strains at selected positions thereon; and said firsttransducer means include at least one strain gage mounted on one of saidselected positions and cooperatively arranged for responding to suchenhanced strains.

14. The load-sensing apparatus of claim 12 wherein the other end of saidstrip-like segment is secured against vertical movement so thattorsional forces imposed on said rounded segment tending to tilt saidstrip-like segment will develop enhanced strains at selected positionsthereon; and said second transducer able loop for defining an enclosedchamber therearound; and

pressure-equalizing means on said load-bearing body and cooperativelyarranged for maintaining said enclosed chamber at an elevated pressureat least about equal to the pressure of drilling fluids in saidlongitudinal bore.

17. The load-sensing apparatus of claim 16 wherein said rounded segmentis annular so that compressional forces imposed thereon will developenhanced strains at selected positions thereon; and said firsttransducer means include at least one strain gage mounted on one of saidselected positions and cooperatively arranged for responding to suchenhanced strains.

18. The load-sensing apparatus of claim 16 wherein the other end of saidstrip-like segment is secured against vertical movement so thattorsional forces imposed on said rounded segment tending to tilt saidstrip-like segment will develop enhanced strains at selected positionsthereon; and said second transducer means include at least one straingage mounted on one of said selected positions and cooperativelyarranged for responding to such enhanced strains.

19. Apparatus adapted for sensing loads acting on a drill bitdependently coupled to a drill string and operatively arranged forexcavating a borehole and comprisa tubular load-bearing body adapted fortandem coupling in a tubular drill string and having a longitudinal borefor conducting drilling fluids flowing through such drill stringsections;

load-responsive means cooperatively arranged between upper and lowerportions of said loadbearing body and adapted for selectively respondingto compressional loads imposed on said loadbearing body tending to movesaid upper and lower body portions longitudinally in relation to oneanother and to torsional loads imposed on said loadbearing body tendingto move said upper and lower body portions angularly in relation to oneanother, said load-responsive means including a deformable loopcoaxially arranged around an intermediate portion of said load-bearingbody and divided into a circumferentially-spaced pair ofsubstantiallyrounded compressible segments and acircumferentially-spaced pair of elongated strip-like bendable segmentshaving their ends respectively. joined between the adjacent side edgesof said rounded segments, first and second means respectively securingthe upper and lower edges of said rounded segments to said upper andlower body portions for alternatively compressing said rounded segmentsupon longitudinal movement of said upper and lower body portions towardone another and rolling said rounded segments to a tilted position uponrelative angular movement between said upper and lower body portions soas to correspondingly distort said strip-like segments;

first electrical transducer means cooperatively arranged on said roundedsegments and adapted for exhibiting a varying electrical characteristicproportional to the magnitude of compressional forces applied to saidrounded segments; and

second electrical transducer means cooperatively arranged on saidstrip-like segments and adapted for exhibiting a varying electricalcharacteristic proportional to the magnitude of torsional forces appliedto said rounded segments causing distortion of said strip-like segments.

20. The load sensing apparatus of claim 19 wherein each of said roundedsegments is angular so that compressional forces imposed theron willdevelop enhanced strains at selected positions thereon; and said firsttransducer means include at least one strain gage mounted on one of saidselected positions at each of said rounded segments and cooperativelyarranged for responding to such enhanced strains.

21. The load-sensing apparatus of claim 20 wherein said secondtransducer means include at least one strain gage mounted on each ofsaid strip-like segments at a position thereon expected to experiencemaximum distortion and, therefore, enhanced strains.

22. The load-sensing apparatus of claim 19 wherein said deformable loopis interior of said load-bearing 16 body.

23. The load-sensing apparatus of claim 22 further including:

a sleeve member cooperatively arranged within said deformable loop;first and second means cooperatively arranged between the upper andlower end portions of said sleeve member and said load-bearing bodyabove and below said deformable loop for defining an enclosed chambertherearound; and

pressure-equalizing means on said load-bearing body and cooperativelyarranged for maintaining said enclosed chamber at an-elevated pressureat least about equal to the pressure of drilling fluids in saidlongitudinal bore.

24. The load-sensing apparatus of claim 23 wherein each of said roundedsegments is annular so that compressional forces imposed thereon willdevelop enhanced strains at selected positions thereon; and said firsttransducer means include at least one strain gage mounted on one of saidselected positions on each of said rounded segments and cooperativelyarranged for responding to such enhanced strains.

25. The load-sensing apparatus of claim 24 wherein said secondtransducer means, include at least one strain gage mounted on each ofsaid strip-like segments at a position thereon expected to experiencemaximum distortion and, therefore, enhanced strains.

1. Apparatus adapted for sensing loads acting on a pipe string in a wellbore and comprising: a load-bearing body adapted for coupling to astring of pipe; a deformable load-responsive member secured in a normalupright position between longitudinally-spaced portions of saidloadbearing body and having an unrestrained intermediate portion adaptedto deform in response to increases and decreases in axial loads imposedon said load-bearing body tending to move said spaced body portionslongitudinally in relation to one another and to tilt in relation to itssaid normal position in response to torsional loads imposed on saidload-bearing body tending to move said spaced body portions angularly inrelation to one another; first transducer means coupled to saidload-responsive member and having a measurable characteristic adapted tovary in response to deformation of said load-responsive member occurringupon relative longitudinal movement between said spaced body portions;and torque-responsive means including second transducer means coupled tosaid load-responsive member and having a measurable characteristicadapted to vary in response to tilting movements of said load-responsivemember away from its said normal position occurring upon relativeangular movement between said spaced body portions.
 2. The load-sensingapparatus of claim 1 wherein at least one of said measurablecharacteristics is an electrical property; and said first transducermeans include at least one strain gage mounted on said intermediateportion of said load-responsive member and exhibiting a varying range ofsaid electrical property in response to strain variations occurring uponthe deforamtion of said load-response member by axial loads on saidload-bearing body.
 3. The load-sensing apparatus of claim 2 wherein saidtorque-responsive means include a deformable member projecting laterallyfrom said intermediate portion of said load-responsive member andcooperatively arranged to deform in response to tilting movements ofsaid load-responsive member, and said second transducer means include atleast one strain gage mounted on said lateral member and exhibiting avarying range of said electrical property in response to strainvariations occurring upon the deformation of said lateral member bytorsional loads on said load-bearing body.
 4. The load-sensing apparatusof claim 2 wherein said intermediate portion of said load-responsivemember is cooperatively curved and arranged to be strained in proportionto the extent of curvature of said intermediate portion.
 5. Theload-sensing apparatus of claim 4 wherein said torque-responsive meansinclude a deformable member projecting laterally from said intermediateportion of said load-responsive member and cooperatively arranged todeform in response to tilting movements of said load-responsive member,and said second transducer means include at least one strain gagemounted on said lateral member and exhibiting a varying range of saidelectrical property in response to strain variations occurring upon thedeformation of said lateral member by torsional loads on saidload-bearing body.
 6. Apparatus adapted for sensing loads acting on apipe string in a well bore and comprising: a load-bearing body adaptedfor coupling in a string of pipe; a load-responsive member havingaxially-spaced opposite portions respectively securEd betweenlongitudinally-spaced portions of said load-bearing body for normallymaintaining said load-responsive member in an upright position and anunrestrained non-linear intermediate portion cooperatively arranged todeflect in response to axial loads imposed on said load-bearing bodytending to move one of said spaced body portions longitudinally inrelation to the other of said spaced body portions as well as to shiftaway from said upright position in response to torsional loads imposedon said load-bearing body tending to move one of said spaced bodyportions angularly in relation to the other of said spaced bodyportions; first means coupled to said intermediate portion of saidload-responsive member and cooperatively arranged for providing a firstoutput signal proportional to deflections of said intermediate portionof said load-responsive member occurring upon relative longitudinalmovement between said spaced body portions caused by axial loads imposedon said load-bearing body; and second means coupled to said intermediateportion of said load-responsive member and cooperatively arranged forproviding a second output signal proportional to the extent of movementof said load-responsive member away from its said upright positionoccurring upon relative angular movements between said spaced bodyportions caused by torsional loads imposed on said load-bearing body. 7.The load-sensing apparatus of claim 6 wherein said load-responsivemember is interior of said load-bearing body.
 8. The load-sensingapparatus of claim 7 further including: a sleeve member having upper andlower end portions respectively extending between said spaced bodyportions; means cooperating with said upper and lower end portions ofsaid sleeve member for defining an enclosed chamber around saidload-responsive member; and pressure-regulating means cooperativelyarranged on said load-bearing body and adapted for maintaining saidenclosed chamber at an elevated pressure.
 9. The load-sensing apparatusof claim 6 wherein said second means include a laterally-orienteddeformable member secured between said load-bearing body and saidintermediate portion of said load-responsive member and cooperativelyarranged to deform upon movement of said load-responsive member awayfrom its said upright position, and transducer means including at leastone strain gage cooperatively arranged on said deformable member andexhibiting a variable electrical characteristic which is proportional tothe strain developed in said deformable member by deformation thereof.10. The load-sensing apparatus of claim 6 wherein said intermediateportion of said load-responsive member is symmetrically curved away froman axis passing through said axially-spaced portions of saidload-responsive member for producing a concentrated strain at about themid-point of said intermediate portion upon deflection thereof; and saidfirst means include at least one strain gage mounted on about saidmid-point of said intermediate portion and exhibiting a variableelectrical characteristic which is proportional to the strain developedin said mid-point of said intermediate portion.
 11. The load-sensingapparatus of claim 10 wherein said second means include alaterally-deformable member secured between said load-bearing body andsaid intermediate portion of said load-responsive member andcooperatively arranged to deform upon movement of said load-responsivemember away from its said upright position, and transducer meansincluding at least a second strain gage cooperatively arranged on saiddeformable member and exhibiting a variable electrical characteristicwhich is proportional to the strain developed in said deformable memberby deformation thereof.
 12. Apparatus adapted for sensing loads actingon a drill bit dependently coupled to a drill string and operativelyarranged for excavating a borehole and comprising: a tubularload-bearing body adapted for tandem coupling in a tubular dRill stringand having a longitudinal bore for conducting drilling fluids flowingthrough such drill string sections; load-responsive means cooperativelyarranged between upper and lower portions of said load-bearing body andadapted for selectively responding to compressional loads imposed onsaid load-bearing body tending to move said upper and lower bodyportions longitudinally in relation to one another and to torsionalloads imposed on said load-bearing body tending to move said upper andlower body portions angularly in relation to one another, saidload-responsive means including a deformable loop coaxially arrangedaround an intermediate portion of said load-bearing body and dividedinto at least one substantially-rounded compressible segment and atleast one elongated strip-like bendable segment having one end coupledto one side of said rounded segment and extending laterally therefromaround said intermediate body portion, first and second meansrespectively securing the upper and lower edges of said rounded segmentto said upper and lower body portions for alternatively compressing saidrounded segment upon longitudinal movement of said upper and lower bodyportions toward one another and rolling said rounded segment to aninclined position upon relative angular movement between said upper andlower body portions so as to correspondingly tilt said strip-likesegment; first electrical transducer means cooperatively arranged onsaid rounded segment and adapted for exhibiting a varying electricalcharacteristic proportional to the magnitude of compressional forcesapplied to said rounded segment; and second electrical transducer meanscooperatively arranged on said strip-like segment and adapted forexhibiting a varying electrical characteristic proportional to themagnitude of torsional forces applied to said rounded segment.
 13. Theload-sensing apparatus of claim 12 wherein said rounded segment isannular so that compressional forces imposed thereon will developedenhanced strains at selected positions thereon; and said firsttransducer means include at least one strain gage mounted on one of saidselected positions and cooperatively arranged for responding to suchenhanced strains.
 14. The load-sensing apparatus of claim 12 wherein theother end of said strip-like segment is secured against verticalmovement so that torsional forces imposed on said rounded segmenttending to tilt said strip-like segment will develop enhanced strains atselected positions thereon; and said second transducer means include atleast one strain gage mounted on one of said selected positions andcooperatively arranged for responding to such enhanced strains.
 15. Theload-sensing apparatus of claim 12 wherein said deformable loop isinterior of said load-bearing body.
 16. The load-sensing apparatus ofclaim 15 further including: a sleeve member cooperatively arrangedwithin said deformable loop; means cooperative with said sleeve memberand said load-bearing body above and below said deformable loop fordefining an enclosed chamber therearound; and pressure-equalizing meanson said load-bearing body and cooperatively arranged for maintainingsaid enclosed chamber at an elevated pressure at least about equal tothe pressure of drilling fluids in said longitudinal bore.
 17. Theload-sensing apparatus of claim 16 wherein said rounded segment isannular so that compressional forces imposed thereon will developenhanced strains at selected positions thereon; and said firsttransducer means include at least one strain gage mounted on one of saidselected positions and cooperatively arranged for responding to suchenhanced strains.
 18. The load-sensing apparatus of claim 16 wherein theother end of said strip-like segment is secured against verticalmovement so that torsional forces imposed on said rounded segmenttending to tilt said strip-like segment will develop enhanced strains atselected positions thereon; and said second transducer means include atleast one strain gage mounted on one of said selected positions andcooperatively arranged for responding to such enhanced strains. 19.Apparatus adapted for sensing loads acting on a drill bit dependentlycoupled to a drill string and operatively arranged for excavating aborehole and comprising: a tubular load-bearing body adapted for tandemcoupling in a tubular drill string and having a longitudinal bore forconducting drilling fluids flowing through such drill string sections;load-responsive means cooperatively arranged between upper and lowerportions of said load-bearing body and adapted for selectivelyresponding to compressional loads imposed on said load-bearing bodytending to move said upper and lower body portions longitudinally inrelation to one another and to torsional loads imposed on saidload-bearing body tending to move said upper and lower body portionsangularly in relation to one another, said load-responsive meansincluding a deformable loop coaxially arranged around an intermediateportion of said load-bearing body and divided into acircumferentially-spaced pair of substantially-rounded compressiblesegments and a circumferentially-spaced pair of elongated strip-likebendable segments having their ends respectively joined between theadjacent side edges of said rounded segments, first and second meansrespectively securing the upper and lower edges of said rounded segmentsto said upper and lower body portions for alternatively compressing saidrounded segments upon longitudinal movement of said upper and lower bodyportions toward one another and rolling said rounded segments to atilted position upon relative angular movement between said upper andlower body portions so as to correspondingly distort said strip-likesegments; first electrical transducer means cooperatively arranged onsaid rounded segments and adapted for exhibiting a varying electricalcharacteristic proportional to the magnitude of compressional forcesapplied to said rounded segments; and second electrical transducer meanscooperatively arranged on said strip-like segments and adapted forexhibiting a varying electrical characteristic proportional to themagnitude of torsional forces applied to said rounded segments causingdistortion of said strip-like segments.
 20. The load sensing apparatusof claim 19 wherein each of said rounded segments is angular so thatcompressional forces imposed theron will develop enhanced strains atselected positions thereon; and said first transducer means include atleast one strain gage mounted on one of said selected positions at eachof said rounded segments and cooperatively arranged for responding tosuch enhanced strains.
 21. The load-sensing apparatus of claim 20wherein said second transducer means include at least one strain gagemounted on each of said strip-like segments at a position thereonexpected to experience maximum distortion and, therefore, enhancedstrains.
 22. The load-sensing apparatus of claim 19 wherein saiddeformable loop is interior of said load-bearing body.
 23. Theload-sensing apparatus of claim 22 further including: a sleeve membercooperatively arranged within said deformable loop; first and secondmeans cooperatively arranged between the upper and lower end portions ofsaid sleeve member and said load-bearing body above and below saiddeformable loop for defining an enclosed chamber therearound; andpressure-equalizing means on said load-bearing body and cooperativelyarranged for maintaining said enclosed chamber at an elevated pressureat least about equal to the pressure of drilling fluids in saidlongitudinal bore.
 24. The load-sensing apparatus of claim 23 whereineach of said rounded segments is annular so that compressional forcesimposed thereon will develop enhanced strains at selected positionsthereon; and said first transducer means include at least one straingage mounted on one of said selected positions on each of said roundeDsegments and cooperatively arranged for responding to such enhancedstrains.
 25. The load-sensing apparatus of claim 24 wherein said secondtransducer means include at least one strain gage mounted on each ofsaid strip-like segments at a position thereon expected to experiencemaximum distortion and, therefore, enhanced strains.